A network provides an infrastructure that facilitates communication between electronic systems, or computer systems, associated with end users. Internetworking protocols allow for the transfer of communication between two or more individualized networks. As such, smaller, individualized networks, such as, local area networks (LAN), are combined into a larger internetwork capable of providing communication services to an ever increasing number of end users. For example, the Internet is a global interconnection of individual networks.
Network devices are hardware devices that facilitate communication through a network. For example, the heart of a network typically includes hubs, switches, routers, access servers, and firewalls. The hub acts as a central point to host computers associated with end users in a local network. As such, the host computers and the hub make up a LAN segment. A switch connects the host computers of a particular LAN to an internetwork of a collection of LANs. The switch provides for a single switched virtual circuit to facilitate communication between two host devices through a larger internetwork across two or more LANs. Access servers connect remote users that are not part of any network to one or more networks. Firewalls act as checkpoints that check message traffic for harmful and unwanted data before routing the traffic through. Routers are intelligent devices that forward message traffic based on the Internet protocol (IP) addresses provided.
Upgrades to software that are used for implementing specific features or services as provided by a network device are necessary to capture new features, enhancements, and fixes to programming errors. For example, software upgrades are implemented when customers want or need new and additional features added to their existing software applications. Also, solutions to specific programming errors require an upgrade to their existing software applications.
However, under traditional approaches, a significant impact on the availability of a network device occurs when upgrading associated software. In general, hardware associated with the network device needs resetting and the network device requires rebooting to initialize upgrades to software associated with a network device. This network device downtime problem occurs also when resetting the network device after a general failure that does not require any software upgrades. As a result, downtime of a particular network device impacts the capability of an associated network to pass communication (e.g., network traffic).
In particular, delays occurring during the installation of upgrades, or during a reset of software, in one example, can be attributed to the loading of the software image code and the resetting of hardware components associated with the network device. Because of these issues, the network device with software to be upgraded may be cutoff from an associated network. This leads to termination of current network traffic held between the network device that is being upgraded and other network devices.
Specifically, prior art methods brought the network device down from the network when installing the software image. The software image comprises the programming code for the upgrade or reset of software that runs a network device. In some cases, the software image is transferred from a secondary device, such as, a hard disk, floppy disk, CDROM, etc. In other cases, the software image is downloaded from a server through the network. For example, the software images can be loaded from flash cards, disks, or from a trivial file transfer protocol (TFTP) server via a network.
Also, prior art methods required at least a minimum reset of many hardware components associated with the network device. As such, hardware components are reset during an upgrade to the software, and the network device is rebooted from scratch in order to initialize the upgraded software images. As a consequence, delivery of network traffic may be interrupted during the hardware reset.
In both cases, these may lead to the physical layer of a network going down. Consequently, a disruption would impact the proper forwarding of network traffic during the software upgrade procedure. This effect may, in one example, spread to upper layers in a network or communication session, resulting in route flaps, traffic loss, etc. These other network devices may undergo disruptions as a result of the termination of the communication session, thereby proliferating further delays throughout a network due to network device downtimes. Since the availability of a network device is critical and software upgrades are necessary, it is important to reduce the downtime of a network device during a software upgrade.
To address these concerns, in one prior art approach, a software upgrade is performed on a monolithic address space system by first loading the upgrade software into a temporary location before initiating the actual upgrade process. Secondly, a minimal reset of hardware components may be performed. This is because, many components will generate interrupts which will make certain portion(s) of the operating code to be accessed. During the upgrade process, the operating code will not be available, resulting in unexpected behavior. Boot strap code is utilized to overwrite the old software image with the new software image. Then new image is then “jumped into” and starts executing. Next, the operations of the hardware components are resumed.
However, this approach is unable to perform an in-service software upgrade. Moreover, this approach is not suitable to be applied to microkernal environments. Specifically, this approach still requires a minimal reset of hardware, a termination of all application processes running on the network device, and a restart of the kernel of the network device. Consequently, this prior art approach still causes forwarding outages and interruptions in network traffic communication.